A longtime friend who lives in Europe e-mailed me recently while on an international aid assignment in Santa Domingo to ask if I knew about the “precautionary principle.”“It is something that is deeply rooted now in European peoples’ minds,” he wrote. “It seems that it is not very popular in the U.S.A.”Yes, I did know and even casually followed related developments, I answered.But it is a concept with very little currency here, I thought at the time. And why is that?First, for those unfamiliar with the term, the precautionary principle, although relatively simple to grasp, has been defined in many ways. Perhaps it is most commonly used in the an environmental context in which the operative word, “precautionary,” simply means, “be careful.”The truism that every parent teaches a child is, “Better safe than sorry.”On a personal level, I discovered early in life that I needed to practice caution, to leave myself a “margin of safety,” even in the most ordinary circumstances.When promoted to the level of a “principle,’ the precautionary idea becomes a little more complicated, as in the Rio Declaration of 1992, an early attempt to build a foundation for global environmental policies.The precautionary approach cited in Principle 15 of that document advises, “Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation.”Sometimes this is simplified to, “Don’t wait for scientific certainty before acting on a threat.”This train of thought made such obvious common sense that the precautionary principle went on to find a place in other international treaties and charters. It has become a central idea in the discussions about global warming and climate change among many other issues at the boundaries between technology and human and environmental health and safety.From arguments about genetically modified organisms to land use to nanotechnology, the precautionary principle is a valuable tool for approaching unknown terrain.To return, then, to the original question one can see very quickly that the “precautionary principle” hangs out with a very alien crowd of ideas that are officially very unpopular in this country.To define a principle in terms of anything “international,” anything “environmental” not to mention restrictive, risk-averse or even a wee bit regulatory goes completely against the grain of official America at this time.To challenge science as the arbiter of such matters is also heretical, although science has compromised itself as a “commodity” when it becomes co-opted for political purposes.According to advocates, the precautionary principle can cleanse science to play a more honest role in solving the immense challenges of the world.Then again, in some areas it may be too late for precaution.On the issue of global warming, some now speak of the post-cautionary principle.In a paper for the Georgetown Law Review, Law Professor Lisa Heinzerling writes, “The irony, even tragedy, in this is that the precautionary principle swept onto the climate change scene at the same moment it could have, and should have, departed the field.”Her point is that when scientists reached a consensus in 1980 in the First Annual Report of the International Panel on Climate Change that it was likely that the planet would heat up by several degrees by 2050, we were already past the precautionary phase. By most accounts related to climate change, the complexion has only gotten worse.The latest IPCC report, with its final volume out this month, says the prognosis is “unequivocal” – not only is there little uncertainty any more, but there is hardly any doubt.“Unfortunately, we long ago frittered away climate change’s precautionary period,” writes Heinzerling.What is bad enough is bound to come. The only question is can we cope with that and still avoid the worst that can happen.The U.S.A. ignores the precautionary principle at its own peril.